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Dec 222008

The work has helped Audubon identify the birds most in need of help, such as the Evening Grosbeak (pictured above; photo credit: Dave Menke) which has declined by 78 percent due to habitat loss in its nesting grounds in Canada as well as other threats in the U.S. over the last 40 years. The Grosbeak is number two on Audubon’s list of Common Birds in Decline. Others on the list include such well-known birds as the Common Tern, the Rufous Hummingbird and the Whip-poor-will.

The lark sparrow, known for its complex songs and whose range extends across the U.S., has landed on the list, threatened by suburban development, invasive species and mining and drilling activities; along with it, another song bird, the horned lark, which likes to nest on bare ground, making it vulnerable to agricultural and urban development activities. (See the Lark Sparrow, pictured right; Photo credit: Glen Tepke.)

The count documents where birds are from year to year, says LeBaron. “It tells us which birds have changed their geographic ranges.” For example, he says, pesticides like DDT can affect where a species might locate.

“Birds are sensitive to changes in the environment. They will leave their habitats if environmental changes affectt hem physically.” DDT, which is used as a pesticide for crops, has been illegal in North American since the ‘70s, but is still used in South America.

In the U.S., DDT remains inextricably tied with the story of the Bald Eagle, the national symbol that was driven nearly to extinction by the pesticide.

DDT’s devastating effects on song birds also illustrated the “power of birds to signal danger and inspire action,” writes John Flicker, current president of Audubon. In an article about the Christmas Bird Count, Flicker cites the work of environmentalist Rachel Carson, whose book Silent Spring brought to light the effects of pesticides on birds and helped launch the modern green movement.

“We (Audubon members) believe that we all share a responsibility to take care of this planet as our home, and that our health, safety, and future are threatened when people damage our environment,” Flicker writes.

The latest environmental threat, global warming, can greatly affect birds, by diminishing available habitat and through extreme weather events, Lebaron said.

“Global climate change puts more energy into the system, creating more weather extremes as the upper layers of the atmosphere get degraded,” he says. Climate change has a negative effect on the birds’ breeding season. Hurricanes, for example, can make it difficult for birds to fly south for their fall migration. Storms like Katrina and Rita destroyed habitats and radically altered breeding seasons for birds on the Gulf Coast, he says.

The sharp-tailed sparrow, known as a coast marsh breeder, is one species that’s been affected by climate change. When the sea level rises, their habitat is endangered, so they relocate. (This species is not counted in the Christmas Count, but in the late winter count since it needs to be done during the breeding season.)

The Christmas Bird Count has become an invaluable tool to scientists, says LeBaron, especially in the past 10 years. Now all the data from every count since 1900 is available in one large database. And with today’s computer technology, the compilers can input the data themselves.

In addition to the Christmas Bird Count, which covers the early winter, there are two other times of year that birds are counted, says LeBaron. The Great Backyard Bird Count, conducted over Presidents’ Weekend in mid February, helps get a snapshot of the end of winter. It is co-sponsored by the Cornell Lab of Ornithology and the Audubon Society.

And Project Feeder Watch, sponsored by Cornell, runs from November to April and counts birds at feeders over four-hour increments.

Wise management and laws, such as the Endangered Species Act of 1973, have helped keep bird populations intact, says LeBaron. As long as the threats to bird life are controlled, birds will thrive.

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